JP3341326B2 - Frame synchronization method and transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frame synchronization method used in transmission systems such as a backbone transmission system, a public network, and a subscriber system.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram of a system to which a conventional frame synchronization method is applied. In the figure, reference numeral 1 denotes a multiplexing device that enables high-speed data transmission by time division multiplexing, 2 denotes a substrate built in the multiplexing device, and a line card that multiplexes each data and transmits the multiplexed data at a high speed. Is a high-speed line for transmitting such data, 4 is a substrate built in the multiplexing apparatus, and in particular, a FAX card installed so as to be suitable for transmission between facsimile apparatuses, 5, 51 to 55
Is a board built in the multiplexing apparatus 1, and the data terminal 6 and the line card 2 or the facsimile apparatus 8 and the FA
A terminal card 7 serving as an interface with the X card 4 is a PB provided between the facsimile device 8 and the multiplexer.
X device.

FIGS. 9A and 9B are diagrams for explaining frame synchronization in this system. FIG. 9A shows data output from the FAX card 4, and FIG. 9B shows data on the high-speed line 3. . In the figure, F1 to F3, f1 to f4
Indicates a synchronization bit, and data (51) to (55) indicate
These are data from the data terminal 6 or the facsimile machine 8 connected to the terminal cards 51 to 55 in FIG.

[0004] Transmission between the facsimile machines 8 will be briefly described. First, data transmitted from the facsimile device 8 is input to the multiplexing device 1 after being processed by the PBX device 7. In the multiplexing apparatus 1, the data is sent to the FAX card 4 via the terminal card 5 and subjected to a process specific to facsimile transmission. The output from the FAX card 4 has a data configuration as shown in FIG. 9A, and has a frame format including many subframes. In addition, synchronization bits F1 to F3 are inserted in the frame. Thereafter, this data is input to the line card 2, processed, and time-division multiplexed with data from each data terminal 6. At this time, data transmitted from the facsimile machine 8 is located in a specific frame (53). The data output from the multiplexer 1 is as shown in FIG.

FIG. 10 shows, for example, Japanese Patent Application Laid-Open No. 62-15993.
FIG. 10 is a diagram showing a conventional frame configuration shown in Japanese Patent Publication No. 3 and corresponding to FIG. In the figure, one frame is composed of L subframes, each subframe is composed of I bits, and a frame pattern is inserted one bit at a time in the leading one bit of each frame. Fi (i = 1,2, ...
L) indicates a frame bit inserted into the first bit of each subframe, and # 1 to #L indicate subframes in I-bit units.

Next, the operation will be described. Fi (i = 1
, 2 ,. . . , L) is a frame pattern. In synchronization detection, (F1,
F2, F3,..., FL-1, FL) are detected to detect synchronization. It is not necessary to insert the frame pattern into all of the frame bits F1 to FL. For example, if the frame pattern is composed of the frame bits F1, F3, F5. . . , The remaining frame bits F2, F4, F6. . . It is also possible to transmit information such as a transmission path monitoring monitor and a service monitor by using.

[0007]

Since the conventional frame is configured as described above, at least I × L bits must be checked to detect a synchronization pattern. In addition, when protection is applied to prevent an information bit from being detected as a synchronization pattern by mistake, it is necessary to check frames for the number of protected stages, and it takes time to detect synchronization. was there. In particular, in the case of a facsimile apparatus, since transmission is performed via a PBX apparatus, there is a disadvantage that the connection is rejected unless synchronization is quickly established.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to enable early detection of synchronization.

[0009]

A frame synchronization method according to the present invention has a continuous frame synchronization pattern at the beginning of a frame according to the start of transmission, and sets all other bits to 0.
Alternatively, a special synchronization frame of 1 is transmitted, and thereafter, a normal synchronization frame including a subframe to which the separated frame synchronization pattern is assigned is transmitted.
The transmission device according to the present invention realizes such a frame synchronization method.

[0010]

According to the frame synchronization method of the present invention, since the frame synchronization pattern in the special synchronization frame transmitted first is not separated, synchronization can be established in a short time transmission.

[0011]

【Example】

Embodiment 1 FIG. Hereinafter, an embodiment of the present invention, particularly, a case of facsimile transmission via a multiplexing device will be described.
FIG. 1 is a configuration diagram of a special synchronization frame. In FIG. 1, one frame is composed of L subframes, and each subframe is composed of I bits. At the beginning of the frame, there is a special synchronization of bits, and all other bits are “0”. FIG. 2 is a sequence diagram showing a method for establishing synchronization according to the present invention.

Next, the operation will be described. As shown in FIG. 2, when station A wants to communicate with station B, it first sends the special synchronization frame of FIG. The station B constantly checks the received data. When detecting the special synchronization, the station B knows that there is a communication request from the station A and can immediately determine the frame head position of the station A. Next, station B informs station A that it has detected special synchronization.
Since the special synchronization frame is sent back at the timing of the station,
The A station knows that the B station has recognized this transmission request, and can also determine the frame start position of the B station. The A station sends out the conventional separated synchronization pattern shown in FIG. 10 to notify the B station that the frame start position of the B station has been determined. When the station B detects the conventional separated synchronization pattern, the station B knows that the station A has determined the start position of the frame, and
The station also sends a conventional separated synchronization pattern. After that, the same communication as before is performed for synchronization.

Embodiment 2 FIG. In the above embodiment, n-bit special synchronization is used to determine the frame head position. However, when there is little noise on the transmission path, only one bit is "1" as shown in FIG. Alternatively, the detection time is shorter.

Embodiment 3 FIG. In addition, as shown in FIG. 4, "1" may be set only for a certain section, and the same effect is obtained.

Embodiment 4 FIG. FIG. 5 is a configuration diagram of a system to which the frame synchronization method according to the present invention is applied. In the figure, 1 to 3 and 5 to 8 represent the same or corresponding parts as in FIG. 9 is an F that realizes the frame synchronization method according to the present invention.
It is an AX card. A description will be given of data transmission between facsimile apparatuses which are required to establish synchronization earlier than between multiplexing apparatuses. In conventional data transmission, data having a configuration as shown in FIG. 9A is transmitted from the start of transmission, whereas according to the present invention, data is transmitted from a special synchronization frame. This special synchronization frame is, for example, “10
It consists of a bit string of 25 bits including 8 bits of “110001” and 17 bits of all “0”, and is generated on the FAX card 9.

FIG. 6 is a block diagram of a part related to data transfer on the FAX card 9. In the figure, reference numeral 91 denotes a so-called TX FIFO (first in first).
out), a shift register on the transmitting side called
Reference numeral 92 denotes a transmission control unit that controls the transmission, 93 denotes a state management unit that manages a control state, and 95 denotes a so-called RX FIFO.
A shift register on the receiving side called O (first in first out), 96 is a transmission data line through which transmission data is conducted, and 97 is a reception data line through which reception data is conducted. In this embodiment, the transmission control unit 92, the state management unit 93, and the reception control unit 94 use a large-capacity PLD (Programmable Logic Dev).
ice), and can also be made into an LSI.

Next, the operation will be described. When transmitted from the facsimile machine 8 on the low-speed line side, first, a synchronization signal is output from the state management unit 93 through the transmission control unit 92. Then, the exchange of the special synchronization and the normal synchronization as described above is performed, and after the synchronization is established, data transmission is performed. Facsimile machine 8, P via low-speed line
The transmission data input from the BX device 7 is
6 is conducted, and is input to the transmission control unit 92 and then to the shift register 91. In the shift register 91, the input clock signal (FYIN
T), an output clock signal (FYOU) generated one subframe later than the input clock signal.
In response to T), the signal is output to the transmission control unit 92 again, and is output from the transmission control unit 92 to a high-speed line. Where IR2Q
Is a signal that becomes 1 if there is at least one free data, OR
2Q is a signal that becomes 1 if there is at least one data,
RF2 is a reset signal. SACM is a line clock signal assigned to this FAX card, used for transmission timing, and
MFP and RXMFP are transmission / reception multi-frame pulses, respectively, and are used to delimit frames. R
ACM is used for reception timing on a line,
KYTD is a low-speed clock.

On the other hand, when data is received from the facsimile machine 8 connected via the high-speed line 3 and the multiplexing apparatus 1 (not shown), synchronization is first established by the state management unit 93 in the same manner as in the above-described transmission. The data is received by the shift register 95 and the reception control unit 94 on the reception side via the data line 97. The detailed operation is the same as that at the time of transmission.

Next, a state transition diagram is shown in order to describe the state management section 93 in more detail in the synchronous frame method of the present invention. In the figure, MODE selects either special synchronization or normal synchronization or both, and specifically, when MODE = 01, only special synchronization is transmitted, and M
When ODE = 11, both special synchronization and normal synchronization are transmitted, and when MODE = 10, only normal synchronization is transmitted. P1 and P2 indicate the number of protection stages, and change in a binary number when synchronization is lost. S and N indicate that special synchronization and normal synchronization have been achieved, respectively, and SF and NF indicate that special synchronization and normal synchronization have not been achieved, respectively. In this embodiment, one frame is composed of 20 subframes each having 25 bits. Also, special synchronization is
The first 8 bits are “10110001” and the remaining 17 bits are all “0” subframes.

In step 1, no synchronization is sent, and the process unconditionally proceeds to step 2. In step 2, only the special synchronization is transmitted. In particular, in this case, by transmitting the special synchronization in two subframes, the probability of erroneously detecting synchronization can be reduced. If the synchronization is established in step 2, the process proceeds to step 30. In step 30, the special synchronization and the normal synchronization are transmitted. Specifically, one subframe of special synchronization and eight subframes of normal synchronization and 11 subframes including all “0” in total of 20
Are transmitted as one frame. Here, data transmission is not yet performed. And NF *
If only the special synchronization is obtained as shown by S and the normal synchronization is not obtained, the process remains at step 30. On the other hand, if the special synchronization has not been achieved, the process proceeds to step 31. In this case, both the special synchronization and the normal synchronization are transmitted as in step 30, but P2P1 indicating the number of protection stages is incremented to 01. At this stage, if only special synchronization is obtained, the process returns to step 30, and if normal synchronization is obtained, the process proceeds to step 4. If the special synchronization has been lost, the process proceeds to step 32. In step 32, both the special synchronization and the normal synchronization are transmitted, and P2P1 indicating the number of protection stages is incremented to 11. Here, if only the special synchronization is obtained, the process returns to step 30, and if the normal synchronization is obtained, the process proceeds to step 4. On the other hand, if special synchronization cannot be obtained, the process returns to step 2.

In step 4, since the synchronization has been established in steps 1 to 3, data transmission is performed, and only normal synchronization is transmitted. Therefore, if the normal synchronization is not lost thereafter, the normal synchronization is repeated. When the normal synchronization is lost, the process proceeds to step S5. In step 5, as in step 4, only normal synchronization is transmitted. If the normal synchronization is lost, the process proceeds to step S6. If the normal synchronization is obtained in steps 5 and 6, the process returns to step 4 and normal data transmission is continued. On the other hand, if the normal synchronization cannot be achieved in step 6, the process returns to step 1 and the process is restarted from the special synchronization. By doing so, synchronization can be performed efficiently and accurately.

In the above-described embodiment, the wired communication is mainly described. However, the present invention is not limited to this, and can be applied to wireless communication. In the fourth embodiment, transmission between facsimile terminals has been described, but transmission between multiplexing devices may be used. In short, any transmission having a multi-frame structure may be used.

[0023]

As described above, according to the present invention, the special synchronization is sent until the start position of the frame is determined, so that the detection time is shortened and the special synchronization pattern is changed to the conventional separated synchronization. If the same pattern is used, the synchronous pattern detection circuit can be used also, so that the circuit does not need to be large. Further, if such a frame synchronization method is used for transmission between facsimile apparatuses, it is possible to respond to a request for early synchronization establishment.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a special synchronization frame according to an embodiment of the present invention.

FIG. 2 is a sequence diagram showing a frame synchronization method according to one embodiment of the present invention.

FIG. 3 is a configuration diagram of a special synchronization frame showing another embodiment of the present invention.

FIG. 4 is a configuration diagram of a special synchronization frame showing another embodiment of the present invention.

FIG. 5 is a configuration diagram of a system to which a frame synchronization method according to one embodiment of the present invention is applied;

FIG. 6 is a block diagram of a FAX card in the system to which the frame synchronization method according to one embodiment of the present invention is applied;

FIG. 7 is a state transition diagram of a frame synchronization method according to an embodiment of the present invention.

FIG. 8 is a configuration diagram of a system to which a conventional frame synchronization method is applied.

FIG. 9 is a configuration diagram of a conventional frame.

FIG. 10 is a configuration diagram of a conventional frame.

[Explanation of symbols]

 1 Multiplexer 8 Facsimile machine

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 7/08 H04J 3/06

Claims (6)

(57) [Claims] 1. In a digital transmission system for transmitting a frame divided into a plurality of subframes, a continuous frame synchronization pattern is provided at the head of a frame according to the start of transmission from a transmission side, and all other bits are set to 0 or 1. Transmitting a special synchronization frame, and extracting a frame synchronization pattern in the special synchronization frame on the receiving side; and transmitting a normal synchronization frame including a subframe to which the frame synchronization pattern separated from the transmission side is assigned. Transmitting and extracting the frame synchronization pattern in the normal synchronization frame on the receiving side. 2. The frame synchronization method according to claim 1, wherein a frame synchronization pattern in the special synchronization frame and a frame synchronization pattern in the normal synchronization frame are the same. 3. In a digital transmission system for transmitting a frame divided into a plurality of subframes, a special synchronization in which a continuous frame synchronization pattern is provided at the beginning of the frame according to the start of transmission and all other bits are set to 0 or 1 A transmission apparatus comprising: means for transmitting a frame; and means for transmitting a normal synchronization frame including a subframe to which a separated frame synchronization pattern is assigned. 4. In a digital transmission system for transmitting a frame divided into a plurality of subframes, a continuous frame synchronization pattern is provided at the beginning of the frame, and all other bits are set to 0 or 1 in a special synchronization frame. A transmission apparatus comprising: means for extracting a frame synchronization pattern; and means for extracting a frame synchronization pattern in a normal synchronization frame including subframes to which a separated frame synchronization pattern is assigned. 5. The transmission apparatus according to claim 3, wherein the transmission apparatus is connected to a facsimile apparatus and used for transmission between the facsimile apparatuses. 6. The transmission device according to claim 3, wherein the transmission device is a multiplexing device.